Optical sensing technology has been used to locate and track movement of objects in multiple dimensions. Traditional optical position sensitive detectors use optical lenses to focus incident light on a particular area of the detector to determine an angular location of an object emitting or reflecting the light. The lenses focus and map light rays emitting from the object to a particular location on the surface of the sensor. The angular location of the object emitting the light may be calculated from the mapped location of the light rays at the sensor and the properties of the lens. While lenses were needed to focus the light on a particular area of the detector in order to measure the properties of the light emitted from a light source, the use of lenses in these detectors has several limitations.
First, optical lenses are required to be positioned at a height at least equal to the focal length of the lens above the light detecting surface. This required separation between the lens and the light detecting surface consumes extra space in electronic devices, which makes it difficult to reduce the size of the device. Second, the lenses also represent a cost component of a detector. Eliminating the lens from these detectors would therefore reduce the height of the detectors and make them less costly to manufacture.
Existing lens-less detector solutions used two or more photodetectors isolated from each other by a trench between them. The trench was aligned with an aperture so that the quantity of incident light reaching each of the photodetectors after passing through the aperture would change as the angle of the incident light on the aperture changed. However, the trench reduced the light collection efficiency of these photodetectors because the light passing through the aperture that reaches the trench would not be detected by the photodetectors. In micromechanical devices, the trench may be several microns wide and may reduce the light collection efficiency of the photodetectors by 10% to 50% depending on the slit width. Additionally, trenches have been difficult to manufacture on germanium based epitaxial layers, which provide improved light detection capabilities over silicon based epitaxial layers.
Accordingly, there is a need for trenchless optical detectors generating an output used to calculate angular information about a light source.